1. Field
The present general inventive concept relates to an image forming apparatus, and more particularly, to a fusing device and method using induction heating and an image forming apparatus including the fusing device.
2. Description of the Related Art
FIG. 1 is a schematic diagram illustrating processes of an electro photographic type printer system. An electrostatic latent image is formed on the surface of an optical OPC drum 10 by electrifying the OPC drum 10 (operation 1) and then exposing the surface thereof (operation 2). Then, the electrostatic latent image formed on the OPC drum 10 is developed into a toner image (operation 3). The toner image is transferred on a print medium (operation 4), and the toner image transferred onto the print medium is fused onto the print medium through fusing (operation 7). When the fusing is finished, erasing is performed (operation 6) after cleaning the toner remaining on the OPC drum 10 (operation 5).
In the fusing operation, the toner image is fused onto the print medium by heat and pressure between a fusing belt/roller and a pressure roller. A method of heating a fusing belt/roller by using a halogen lamp or an induction heating method is mainly used as a heating method. In the induction heating method, since only the surface of the fusing belt/roller is heated, it is possible to reduce a time necessary to raise the temperature of a fuser (not shown) compared to the method of heating the fusing belt/roller by using a halogen lamp.
In the induction heating method, since the heating belt/roller is heated by an induction current that is generated by an inductor composed of an induction coil and a ferrite, the elements of the fusing belt/roller is formed of a magnetic material such as nickel or Steel Use Stainless (SUS) 430. However, when an internal coil type induction heating method is used, an induction coil in an induction heating (IH) fuser is located inside a heating roller, similar to the method of heating by using a halogen lamp. A large period of time is required for heat generated from an internal heating element to reach the surface of the heating roller, and the cost may increase since the induction coil, which is generally expensive, and the ferrite should be replaced together with the heating roller when the heating roller needs to be replaced.
In order to overcome this shortcoming, an external coil type induction heating method in which an inductor composed of an induction coil and a ferrite is located outside a heating roller is mainly used in the IH fuser. In the external coil type induction heating method, only the heating roller may be replaced without replacing the expensive inductor when it is necessary to replace a fuser.
As illustrated in FIG. 2, in a fuser using the external coil type induction heating method in which an induction coil is disposed outside a heating roller, the induction coil is rolled in a horseshoe-like shape at both ends of the heating roller. Due to this, the heating performance of the both ends of the heating roller is deteriorated, and it is necessary to increase the length of the heating roller/belt compared to the method of heating by using a halogen lamp. As a result, the length of the heating roller/belt of the IH fuser is increased compared to other type fusers, and thus, a printer employing the IH fuser becomes larger.
In addition, in the induction heating method, since the heating belt is thin, heating an area of the heating belt on which a printing paper passes is transmitted to the printing paper. Thus, when a printing paper having a small size such as B5 or A6 size that is smaller than A3 size is continuously printed, heat of an area of the heating belt on which the printing paper does not pass is accumulated, Therefore, the temperature of the area of the heating belt on which the printing paper does not pass excessively rises. Thus, the induction heating method is less advantageous than the method of heating by using a halogen lamp in coping with various types of printing papers.